content: package com.alipay.v3;
  
  import java.util.Map;
  
  /**
   * Representing a Server configuration.
   */
  public class ServerConfiguration {
      public String URL;
      public String description;
      public Map<String, ServerVariable> variables;
  
      /**
       * @param URL A URL to the target host.
       * @param description A description of the host designated by the URL.
       * @param variables A map between a variable name and its value. The value is used for substitution in the server's URL template.
       */
      public ServerConfiguration(String URL, String description, Map<String, ServerVariable> variables) {
          this.URL = URL;
          this.description = description;
          this.variables = variables;
      }
  
      /**
       * Format URL template using given variables.
       *
       * @param variables A map between a variable name and its value.
       * @return Formatted URL.
       */
      public String URL(Map<String, String> variables) {
          String url = this.URL;
  
          // go through variables and replace placeholders
          for (Map.Entry<String, ServerVariable> variable: this.variables.entrySet()) {
              String name = variable.getKey();
              ServerVariable serverVariable = variable.getValue();
              String value = serverVariable.defaultValue;
  
              if (variables != null && variables.containsKey(name)) {
                  value = variables.get(name);
                  if (serverVariable.enumValues.size() > 0 && !serverVariable.enumValues.contains(value)) {
                      throw new IllegalArgumentException("The variable " + name + " in the server URL has invalid value " + value + ".");
                  }
              }
              url = url.replaceAll("\\{" + name + "\\}", value);
          }
          return url;
      }
  
      /**
       * Format URL template using default server variables.
       *
       * @return Formatted URL.
       */
      public String URL() {
          return URL(null);
      }
  }
  